The British Standard Pipe thread (BSP thread) is a family of standard screw thread

Screw thread

A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...

 types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external (male

Gender of connectors and fasteners

In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female...

) with an internal (female

Gender of connectors and fasteners

In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female...

) thread.

Types

Two types of threads are distinguished:

• Parallel ('straight') threads, British Standard Pipe Parallel thread (BSPP; originally also known as British Standard Pipe Fitting thread/BSPF and British Standard Pipe Mechanical thread/BSPM), which have a constant diameter; denoted by the letter G.
• Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread; denoted by the letter R.

These can be combined into two types of joints:

• Jointing threads: These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (In Europe, taper female pipe threads are not commonly used.)
• Longscrew threads: These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut.

Thread form

• the threadform follows the British Standard Whitworth
  British Standard Whitworth
  British Standard Whitworth is one of a number of imperial unit based screw thread standards which use the same bolt heads and nut hexagonal sizes, the others being British Standard Fine thread and British Standard Cycle...
  
   standard
• symmetrical V-thread in which the angle between the flanks is 55° (measured in an axial plane)
• one-sixth of this sharp V is truncated at the top and the bottom
• the threads are rounded equally at crests and roots by circular arcs ending tangentially with the flanks
• the theoretical depth of the thread is therefore 0.64 times the nominal pitch

Pipe thread sizes

A list of 16 thread sizes are defined by the standards, ranging from to 6. The size number was originally based on the inner diameter measured in inches of a steel tube for which the thread was intended, but in the modern metric version of the standard is simply a size number.

Dash thread size	Thread size	Threads / in	Pitch (mm)	Thread major diameter		A/F (mm)	Gauge length (mm)		Corresponding pipe				Tapping drill size (mm)
				(mm)	(in)				DN	OD (mm)	OD (in)	Thickness (mm)	BSP.PL (Rp)	BSP.F (G)
	0.0625	28	0.907	7.723	0.304		4						6.60	6.80
−2	0.125	28	0.907	9.728	0.383	15	4		6	10.2	0.40	2	8.60	8.80
−4	0.25	19	1.337	13.157	0.518	19	6		8	13.5	0.53	2.3	11.50	11.80
−6	0.375	19	1.337	16.662	0.656	22/23	6.4		10	17.2	0.68	2.3	15.00	15.25
−8	0.5	14	1.814	20.955	0.825	27	8.2		15	21.3	0.84	2.6	18.75	19.00
−10	0.625	14	1.814	22.911	0.902				16			2.6	-	21.00
−12	0.75	14	1.814	26.441	1.041	32	9.5		20	26.9	1.06	2.6	24.25	24.50
−16	1	11	2.309	33.249	1.309	43	10.4		25	33.7	1.33	3.2	30.40	30.75
−20	1.25	11	2.309	41.910	1.650	53	12.7		32	42.4	1.67	3.2	39.00	39.50
−24	1.5	11	2.309	47.803	1.882	57	12.7		40	48.3	1.90	3.2	45.00	45.00
−32	2	11	2.309	59.614	2.347	70	15.9		50	60.3	2.37	3.6	56.75	57.00
	2.5	11	2.309	75.184	2.960		17.5		65	76.1	3.00	3.6
	3	11	2.309	87.884	3.460		20.6		80	88.9	3.50	4
	4	11	2.309	113.030	4.450		25.5		100	114.3	4.50	4.5
	5	11	2.309	138.430	5.450		28.6		125	139.7	5.50	5
	6	11	2.309	163.830	6.450		28.6		150	165.1	6.50	5

The major diameter listed is the outer diameter of the external thread. For a taper thread, it is the diameter at the "gauge length" from the small end of the thread. The taper is 1 to 16, meaning that for each 16 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.

Pipe thread designations

These standard pipe threads are formally referred to by the following sequence of blocks:

• the words "Pipe thread",
• the document number of the standard (e.g., "ISO 7" or "EN 10226")
• the symbol for the pipe thread type:
  • G = external + internal parallel (ISO 228)
  • R = external taper (ISO 7)
  • Rp = internal parallel (ISO 7/1)
  • Rc = internal taper (ISO 7)
  • Rs = external parallel
• the thread size

Threads are normally right-hand. For left-hand threads, the letters "LH" are appended.

Example: Pipe thread EN 10226 Rp 2½

The terminology for the use of G and R originated from Germany (G for Gas, as it was originally designed for use on gas pipes ; R for Rohr (meaning pipe).)

See also

• AN thread
  AN thread
  The AN thread is a particular type of fitting used to connect flexible hoses and rigid metal tubing that carry fluid. It is a US military-derived specification that dates back to World War II and stems from a joint standard agreed upon by the Army and Navy, hence AN.AN sizes range from -2 to -32...
  
  
• British standard brass thread
  British standard brass thread
  British standard brass thread is an imperial unit based screw thread. It adopts the Whitworth thread form with a pitch of 26 threads per inch for all diameters...
  
  
• Garden hose thread
• National pipe thread
  National pipe thread
  National Pipe Thread Tapered Thread is a U.S. standard for tapered threads used on threaded pipes and fittings. The taper rate for all NPT threads is measured by the change of diameter over distance. The angle between the taper and the center axis of the pipe is 1° 47′ 24″...
  
  

• Panzergewinde
  Panzergewinde
  The Stahlpanzerrohrgewinde standard for screw threads, more often called by the shorter name Panzergewinde , is a technical standard created in Germany and subsequently used in various countries, such as the German-speaking zone and neighboring European countries...
  
  
• Thread angle
  Thread angle
  The thread angle of a screw is the angle between the threads. This is a defining factor for the shape of a screw thread. Standard values include:...
  
  
• Threaded pipe
  Threaded pipe
  A threaded pipe is a pipe with screw-threaded ends for assembly.- Tapered threads :The threaded pipes used in some plumbing installations for the delivery of gases or fluids under pressure have a threaded section that is slightly conical . This is called a "tapered thread"...
  
  

External links

• Newman Tools Inc. and J.W. WINCO, INC. show the Whitworth form BSP or ISO pipe thread.